Limit first 9 moves thinking depth to less than 15

The critical point is set move 9's depth to 14.

1. d6 f4 2. b4 d2 3. b6 f6 4. b2xf6 f6 5. d7
If not set to 14 (15 or above is bad)
Black will do move d5 (bad move)
If change move 9' depth to 14
Black will do move f2xd7 (good move)

src/mills.cpp

@@ -470,8 +470,8 @@ Depth get_search_depth(const Position *pos)
         if (pos->phase == Phase::placing) {
             const Depth placingDepthTable[25] = {
                   +1,  1,  +1,  1,   /* 0 ~ 3 */
-                  +3, 15, +15,  0,   /* 4 ~ 7 */
-                  +0, 0, +0,  0,     /* 8 ~ 11 */
+                  +3, 15, +15, 15,   /* 4 ~ 7 */
+                  +15, 14, +0,  0,   /* 8 ~ 11 */
                   +0, 0, +0,  0,     /* 12 ~ 15 */
                   +0, 0, +0,  0,     /* 16 ~ 19 */
                   +0, 0, +0,  0,     /* 20 ~ 23 */